Refactor chained_path(), add chained_path_items() and chained_path_points()

lib/Slic3r/Fill.pm

@@ -182,10 +182,8 @@ sub make_fill {
     push @fills, @{$layer->thin_fills};
     push @fills_ordering_points, map $_->unpack->points->[0], @{$layer->thin_fills};
     
-    # organize infill paths using a shortest path search
-    @fills = @{chained_path([
-        map [ $fills_ordering_points[$_], $fills[$_] ], 0..$#fills,
-    ])};
+    # organize infill paths using a nearest-neighbor search
+    @fills = @fills[ chained_path(\@fills_ordering_points) ];
     
     return @fills;
 }

lib/Slic3r/Geometry.pm

@@ -7,7 +7,7 @@ our @ISA = qw(Exporter);
 our @EXPORT_OK = qw(
     PI X Y Z A B X1 Y1 X2 Y2 MIN MAX epsilon slope line_atan lines_parallel 
     line_point_belongs_to_segment points_coincide distance_between_points 
-    comparable_distance_between_points
+    comparable_distance_between_points chained_path_items chained_path_points
     line_length midpoint point_in_polygon point_in_segment segment_in_segment
     point_is_on_left_of_segment polyline_lines polygon_lines nearest_point
     point_along_segment polygon_segment_having_point polygon_has_subsegment
@@ -799,29 +799,43 @@ sub polyline_remove_short_segments {
     }
 }
 
-# accepts an arrayref; each item should be an arrayref whose first
-# item is the point to be used for the shortest path, and the second
-# one is the value to be returned in output (if the second item
-# is not provided, the point will be returned)
+# accepts an arrayref of points; it returns a list of indices
+# according to a nearest-neighbor walk
 sub chained_path {
     my ($items, $start_near) = @_;
     
-    my %values = map +($_->[0] => $_->[1] || $_->[0]), @$items;
-    my @points = map $_->[0], @$items;
+    my @points = @$items;
+    my %indices = map { $points[$_] => $_ } 0 .. $#points;
     
-    my $result = [];
+    my @result = ();
     my $last_point;
     if (!$start_near) {
         $start_near = shift @points;
-        push @$result, $values{$start_near} if $start_near;
+        push @result, $indices{$start_near} if $start_near;
     }
     while (@points) {
         $start_near = nearest_point($start_near, [@points]);
         @points = grep $_ ne $start_near, @points;
-        push @$result, $values{$start_near};
+        push @result, $indices{$start_near};
     }
     
-    return $result;
+    return @result;
+}
+
+# accepts an arrayref; each item should be an arrayref whose first
+# item is the point to be used for the shortest path, and the second
+# one is the value to be returned in output (if the second item
+# is not provided, the point will be returned)
+sub chained_path_items {
+    my ($items, $start_near) = @_;
+    
+    my @indices = chained_path([ map $_->[0], @$items ], $start_near);
+    return [ map $_->[1], @$items[@indices] ];
+}
+
+sub chained_path_points {
+    my ($points, $start_near) = @_;
+    return [ @$points[ chained_path($points, $start_near) ] ];
 }
 
 sub douglas_peucker {

lib/Slic3r/Layer/Region.pm

@@ -2,7 +2,7 @@ package Slic3r::Layer::Region;
 use Moo;
 
 use Slic3r::ExtrusionPath ':roles';
-use Slic3r::Geometry qw(scale chained_path);
+use Slic3r::Geometry qw(scale chained_path_items);
 use Slic3r::Geometry::Clipper qw(safety_offset union_ex diff_ex intersection_ex);
 use Slic3r::Surface ':types';
 
@@ -167,7 +167,7 @@ sub make_perimeters {
     my @perimeters = ();  # one item per depth; each item
     
     # organize islands using a shortest path search
-    my @surfaces = @{chained_path([
+    my @surfaces = @{chained_path_items([
         map [ $_->contour->[0], $_ ], @{$self->slices},
     ])};
     
@@ -319,18 +319,24 @@ sub make_perimeters {
     }
     
     # process one island (original surface) at time
+    # islands are already sorted with a nearest-neighbor search
     foreach my $island (@perimeters) {
         # do holes starting from innermost one
         my @holes = ();
         my %is_external = ();
+        
+        # each item of @$island contains the expolygons having the same depth;
+        # for each depth we build an arrayref containing all the holes
         my @hole_depths = map [ map $_->holes, @$_ ], @$island;
         
-        # organize the outermost hole loops using a shortest path search
-        @{$hole_depths[0]} = @{chained_path([
+        # organize the outermost hole loops using a nearest-neighbor search
+        @{$hole_depths[0]} = @{chained_path_items([
             map [ $_->[0], $_ ], @{$hole_depths[0]},
         ])};
         
+        # loop while we have spare holes
         CYCLE: while (map @$_, @hole_depths) {
+            # remove first depth container if it contains no holes anymore
             shift @hole_depths while !@{$hole_depths[0]};
             
             # take first available hole